Franken tells CNN's "State of the Union" that the concern arises "in the way that we all have this suspicion" that "he lies a lot."

Franken cites Trump's groundless claim that he would have won the popular vote in the presidential race if not for 3 million to 5 million immigrants in the country illegally voting for his Democratic opponent, Hillary Clinton.

And Trump is said to have told some senators in a private meeting at the White House that he and former Republican Sen. Kelly Ayotte would have won in New Hampshire if not for voters bused in from out of state.